Background and objective: Weight gain is a common undesirable side effect of insulin treatment in type 1 diabetics. This study tested the assumption that this is due to an increase in fat mass.
Patients and method: Bioelectric impedance measurements were performed on 157 young male and 117 female diabetics (age 17.6 +/- 4.9 years; diabetes duration 8.9 +/- 5.7 years) and the fat-free mass (FFM) calculated according to the equation of Schfer et al. The data of the diabetics were compared with those of healthy controls and normal values published by Barlett et al.
Results: The average weight of the diabetic cohort was 2.0 +/- 0.7 kg higher than in the reference groups, adjusted for sex and age. FFM was higher by 2.9 +/- 0.7 kg in diabetics than in the healthy cohort of Barlett et al (P < 0.005), being equally high in males and females (+2.9 +/- 0.7 kg and 2.9 +/- 0.6 kg, respectively). But compared with the values in metabolically normal controls the percentage fat proportion was lower in the diabetics than the controls, but not significantly (-1.3 +/- 0.6%). Weight gain was greater in females than males (+3.8 +/- 0.9 kg vs +1.2 +/- 0.9 kg, P < 0.05). After correcting for age, there was a partial correlation between good metabolic control and FFM in males. The form of treatment had no effect on body composition.
Conclusion: These data indicate that weight gain in young diabetics is due not to an increase in fatty tissue but in muscle mass. This is probably the result of peripheral hyperinsulinism combined with hyperglycaemia.